1. Field of the Invention
The present invention relates to an ink jet printing apparatus that ejects ink onto a printing medium to print characters and images, and relates particularly to an ink jet printing apparatus wherein a head cartridge that ejects ink and ink tanks are detachably mounted on a carriage.
2. Description of the Related Art
A well-known ink jet printing apparatus is a serial type ink jet printer, i.e., a type wherein a head cartridge, which includes a print head for ejecting ink, is moved in a direction perpendicular to the direction in which a printing medium is conveyed, while simultaneously, ink is ejected from the print head onto the printing medium to form an image. In the serial type ink jet printing apparatus (hereinafter referred to simply as a printing apparatus), a head cartridge and an ink tank, wherein ink to be supplied to the head cartridge is retained, are detachably mounted on a carriage. With this arrangement, the ink tank alone can be replaced when the ink therein has been exhausted, and the print head alone can be replaced when the print head has malfunctioned, and since these procedures are individually performed only as needed, operating costs can be reduced.
High-quality image printing, available even for professional use, has also been requested for an ink jet printing apparatus, and more ink color variations have been developed as one measure for providing high-quality printing. For example, an arrangement wherein, for performing printing, ink tanks of eight to twelve colors have been mounted is employed for a single head cartridge.
Further, as described in Japanese Patent No. 4,333,980, a fixing member is provided for a carriage to secure a head cartridge to the carriage. This fixing member includes a lever having an operating portion and pressure springs that press the head cartridge against the carriage, and secures the head cartridge to the carriage as the lever is pivoted. When the head cartridge is to be released from the carriage, the lever of the fixing member must be pivoted by lifting the operation portion.
However, according to the above described technique, it has been found that when, in response to a high-quality image printing request, the number of ink tanks to be mounted is increased in order to correspond to an ink color variation count, a force applied to hold a head cartridge is reduced. The reason that the holding force for the head cartridge is reduced is as follows.
Specifically, ink supply portions are formed in the bottoms of the individual ink tanks, while a head cartridge has ink inflow portions at positions that are opposed to the individual ink supply portions when the ink tanks are mounted. When the ink tanks are mounted on the head cartridge, the ink supply portions of the ink tanks are connected to the ink inflow portions of the head cartridge to supply ink from the ink tanks to the print heads of the head cartridge. In order to prevent the leakage of ink from the joints of the head cartridge and the ink tanks during the ink supply operation, generally, an arrangement is employed wherein the ink tanks and the head cartridge closely contact each other, by employing, for example, coupling members formed of a resilient material. Therefore, the ink tanks and the head cartridge receive a repulsive force from the coupling members. When the number of ink tanks to be mounted on the print head is increased, accordingly, the total repulsive force the head cartridge receives from the coupling members when the ink tanks are mounted is also increased. As a result, the repulsive force may be greater than the force with which the head cartridge is pressed against the carriage, and the holding force for the head cartridge may become too low to hold and maintain the head cartridge at a predetermined position, and thus, that image forming would be adversely affected.
As one method for resolving this problem, the force applied to press and hold the print head can be increased. However, as a result, a very great operation force is required to mount the head cartridge on the carriage, and the operability is degraded. Furthermore, when the force applied by the pressure springs provided for the fixing portion is to be increased, a special, rigid material must be employed in order to prevent the deformation of the fixing member, and a complicated linking mechanism is also required in order to reduce the operation force of the fixing member.
As another method for resolving the above described problem, a member different from the fixing member is provided for the carriage to increase the holding force for the head cartridge. In this case, however, not only the manufacturing cost for the product is increased, but also a space for mounting the other member is also required, and a new problem will have occurred, in that the size of the entire apparatus is increased.